Superparamagnetic iron oxide as an efficient and recoverable catalyst for rapid and selective trimethylsilyl protection of hydroxyl groups

Abstract

At room temperature and under solvent-free conditions, various types of alcohols and phenols were efficiently protected within a few minutes using hexamethyldisilazane and magnetically recoverable Fe 3 O 4 . Preferential protection of primary alcohols was observed when they competed with secondary or tertiary alcohols. Highly selective protection of phenols in the presence of aromatic amines or thiophenol was also observed.

Oxide Nanomaterials: Synthetic Developments, Mechanistic Studies, and Technological Innovations

“…One of the most straightforward examples is the use of magnetite (Fe 3 O 4 ) nanocatalysts to catalyze the protection of hydroxy groups with trimethylsilyl (TMS) groups. [308] Magnetite and maghemite (g-Fe 2 O 3 ) are easily accessible and inexpensive so that they are most widely used for coreshell approaches to magnetize other catalyst materials. [299] Although the higher saturation magnetization of magnetite makes it the material of choice at first glance, its rapid oxidation into maghemite is a drawback that may furthermore be difficult to detect with X-ray diffraction methods.…”

Oxidische Nanomaterialien: Von der Synthese über den Mechanismus zur technologischen Innovation

“…[308] Magnetit und Maghämit (g-Fe 2 O 3 ) sind leicht zugänglich und günstig erhältlich, sodass sie weithin für die Magnetisierung von Katalysatormaterialien durch die Bildung von KernHülle-Partikeln verwendet werden. [299] Obwohl seine höhere magnetische Sättigung Magnetit auf den ersten Blick als magnetisches Material der Wahl erscheinen lässt, ist seine rasche Oxidation zu Maghämit, die zudem mit konventionellen Röntgenbeugungsmethoden schwierig nachweisbar Abbildung 16. a) Abbildung eines industrieüblichen magnetischen Separators (der Magnet befindet sich in einer Box, die oberhalb des För-derbandes aufgehängt ist); b) magnetische Trennung im Labormaß-stab (1.5-mL-Gefäße); c) Polycarbonat-infiltrierte Bragg-Reflektoren können vom Glassubstrat abgelöst und d) wieder auf einen Si-Wafer übertragen werden.…”

Efficient and Rapid Solvent-Free Acetylation of Alcohols, Phenols, and Thiols Using Catalytic Amounts of Sodium Acetate Trihydrate

“…In the framework of our studies to design ecofriendly synthetic procedures [36][37][38][39] and in continuation of our program to develop efficient procedures for functional groups protection [40][41][42], we recently reported an environmentally benign chemoselective process for spontaneous acetylation of various amines by acetic anhydride at room temperature by using no catalyst or additive [43]. However, under the conditions, thiols were acetylated in a much slower fashion and alcohols remained intact.…”